Complete Sleep Guide — How To Use This Sleep Calculator
This page combines a practical sleep calculator with an in-depth guide that covers sleep cycles, circadian rhythms, bedtime routines, nutrition, naps, common sleep problems, and frequently asked questions. Read the sections that matter to you — use the calculator at the top to test times quickly. This guide is designed to be actionable so you can improve sleep tonight and over the long term.
1. Sleep Science Basics — Sleep Stages & Cycles
Sleep is not a single uniform state — it’s a sequence of repeating stages that together form sleep cycles. Understanding these stages is essential to planning sleep that leaves you feeling refreshed.
1.1 Sleep Stages
There are four main sleep stages commonly described:
- Stage 1 (Light sleep): A transition from wakefulness to sleep; brain activity begins to slow.
- Stage 2: Light sleep but with deeper rest; body temperature drops and heart rate slows. Often considered "light" restorative sleep.
- Stage 3 (Deep sleep): Slow-wave sleep important for